Histamine release in the dog after leukocyte lysate injection.

Mixed leukocyte suspensions, containing 10(6) leukocytes per ml, were prepared from dog peripheral blood by dextran sedimentation. Lysates of these suspensions, prepared by sonification, were administered intravenously to the autologous dogs. The plasma histamine levels were increased to an average value 320% above the control values (P < 0.001). The individual elements in the mixed leukocyte suspensions were separated by sucrose gradient and glass bead column fractionation procedures, and purified suspensions of platelets (no other formed elements present), lymphocytes (95 to 100%), and granulocytes (90 to 98%) were obtained. Lysates of these suspensions all had significant histamine-releasing activity when administered intravenously to dogs. Although leukocytes and platelets from other species are known to harbor mediators of histamine release, this study provides the first demonstration of the histamine-releasing activity of dog leukocytes and platelets. Many of the studies of leukocyte and platelet histamine-releasing factors have employed in vitro systems leaving the in vivo role of these factors in doubt. The present studies provide evidence that leukocyte and platelet histamine-releasing factors have in vivo activity.